How is a Diesel Engine Different to a Petrol Engine?

petrol in a diesel, petrol in diesel

Do you know the difference between diesel and petrol engines? There are many advantages and disadvantages to both.

If you happen to put petrol in a diesel engine or vice versa, you will need a wrong fuel removal expert to remove the fuel for you to avoid damage to the engine. Sydney Fuel Assist can provide you with wrong fuel help, 24/7.

A lot of people have a preference for one type of engine over the other. Here are the main differences:

Diesel Engines

In the past 5 years diesel has had a huge makeover. It has gone from low grade and smelly, mainly suited to trucks, to powering some of the most high performance sports vehicles today.

Sale of diesel powered cars and vehicles has nearly doubled in Australia since 2005. Buyers are enticed by cleaner and more fuel efficient diesel engines. Many of these motors are just as quiet and smooth running as petrol engines.

Some points to consider are:

  • Diesel engines are found in all sorts of vehicles from compact cars to luxury limousines. They are popular now in sporty cars such as Audi and Peugeot too
  • There are more dangerous gases omitted through diesel engines than petrol powered cars however, because they use less fuel than petrol they can emit less CO2 over time
  • The correct type of fuel must be used for each type of engine. Do not drive the vehicle if you accidentally put in the wrong type of fuel. Call Sydney Fuel Assist for wrong fuel help
  • Diesel models of vehicles are more expensive, costing on average around $2,000 more than petrol models
  • Bowser prices have traditionally favoured petrol over diesel but this is changing, particularly now than many cars need to use premium unleaded petrol
  • A diesel engine is generally 20% more efficient than a petrol engine of equivalent size
  • As well as poisonous gases like nitrogen oxide and sulfur oxide, diesel produces diesel particle matter known as black soot. Most diesel vehicles have a filter that captures the soot and burns it off


Diesel cars may cost more to buy but they hold their value more so than petrol vehicles. When you are looking at resale, petrol engines usually have a higher appeal and are priced more reasonable in small and medium cars. When it comes to medium and large SUVS however, diesel is often favoured.

How the Engines Work

The biggest difference between petrol and diesel engines besides the types of fuel they use is how the fuel is ignited.

Petrol Engines

In an older petrol engine a carburetor is used to make a petrol and air mixture that enters the cylinder.

Petrol engines use a spark plug to ignite the fuel inside the cylinder. A petrol engine is generally lighter than a diesel engine as diesel engines are strengthened to cope with extra forces required to compress and ignite the fuel.

Diesel Engines

A diesel engine uses a much higher compression ratio than a petrol engine within the cylinder to heat the air inside. In diesel engines there is a fuel injector for the injection of diesel into the cylinder. The air and fuel enter the cylinder separately.

When fuel is injected into the compressed air, it is ignited with a spark plug. Because of the air compression there is a far greater fuel efficiency.

What Happens if You Put Petrol in a Diesel Engine?

If you mistakenly put petrol in a diesel fuel tank, the mixture of petrol in diesel acts as a solvent. Lubrication is reduced and damage is caused to the pump when metal components connect and rub together. Other components of the fuel system that are not compatible with petrol can also be damaged.


Sydney Fuel Assist are the experts when it comes to fuel cleaning, wrong fuel removal, and all things fuel related. Contact us for wrong fuel help and all your fuel needs.